Thermo-Mechanical Behavior of Steel-Concrete Composite Columns under Natural Fire Including Heating and Cooling Phases

The fire behavior of concrete filled hollow steel sections has been studied extensively in various countries. Almost all essential parameters influencing their resistance have been identified: section shape and dimensions, concrete filling, reinforcement ratio, steel tube thickness, column slenderness, thermal and mechanical properties of steel and concrete, and even the contact problem at the steel-concrete interface. Most of these works were done under standard fire conditions (ISO), which are represented by a continuously increasing temperature over time. It is thus not really a curve reflecting a natural fire which includes not only a heating phase but also a cooling phase during which the temperature of the fire is decreasing back to ambient temperature.In this paper, the behavior of axially loaded concrete filled square hollow section columns subjected to natural fire conditions has been studied. The main objectives of this study are: first, to demonstrate the phenomenon of delayed collapse of this type of columns during or after the cooling phase of a fire, and then study the influence of certain determinant parameters, such as section size, tube thickness, reinforcement ratio, concrete cover and column length.The results show that delayed failures occur for massive sections, small values of the thickness of the steel tube and for the low-slendernes.

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Structural behaviour of concrete filled hollow steel sections exposed to parametric fire

Challenge Journal of Structural Mechanics ◽

10.20528/cjsmec.2017.02.004 ◽

2017 ◽

Vol 3 (4) ◽

pp. 160

Author(s):

Mohammed Salah Dimia ◽

Soumia Sekkiou ◽

Mohamed Baghdadi ◽

Mohamed Guenfoud

Keyword(s):

Steel Tube ◽

Concrete Cover ◽

Critical Conditions ◽

Structural Behaviour ◽

Natural Fire ◽

Composite Columns ◽

Section Size ◽

Fire Scenarios ◽

Steel Sections ◽

Cooling Phase

This article analyzes steel-concrete composite columns subjected to natural fire scenarios in order to verify that the possibility of structural collapse during or after the cooling phase is real. The main objectives of this study are: first, to highlight the phenomenon of delayed collapse of this type of columns during or after the cooling phase of a fire, and then analyze the influence of some determinant parameters, such as section size, tube thickness, reinforcement (ratio), concrete cover and column length. The results show that critical conditions with respect to delayed failure arise for massive sections, small values of the steel tube thickness and for columns with massive section.

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A Computational Model for Prestressed Concrete Hollow-Core Slab Under Natural Fire

International Journal of Concrete Structures and Materials ◽

10.1186/s40069-019-0373-9 ◽

2019 ◽

Vol 13 (1) ◽

Author(s):

R. Pečenko ◽

T. Hozjan ◽

I. Planinc ◽

S. Bratina

Keyword(s):

Computational Model ◽

Prestressed Concrete ◽

Concrete Slab ◽

Hollow Core ◽

Two Phase ◽

Natural Fire ◽

Heating And Cooling ◽

Hollow Core Slab ◽

Cooling Phase ◽

Core Concrete

AbstractPerformance-based approach, introducing a new two-phase computational model for determining the response of prestressed hollow-core concrete slab exposed to natural fire including heating and cooling phase, is presented. Firstly, the two-dimensional coupled hygro-thermo-chemical model is used to determine time dependent temperature and moisture field in the characteristic cross-section of the concrete hollow-core slab during fire. In addition, the influence of opening on the temperature distribution over prestressed hollow-core concrete slab is accounted for. Secondly, stress–strain state of prestressed concrete hollow-core slab is determined with a newly developed one-dimensional geometrical and material non-linear model, which includes a slip between concrete and tendon. Temperature dependent mechanical properties of concrete, tendon and bond stiffness are accounted for in the model. Model validation showed that the presented two-phase computational model is suitable for the analysis of prestressed hollow-core concrete slab exposed to natural fire. Furthermore, parametric studies revealed that heat exchange between the concrete section and the opening has a significant influence on the development of temperatures in the slab, particularly in the cooling phase, and consequently also on the development of slab displacements. In addition, it was identified that accounting for the slip between concrete and tendon enables the determination of the bond stress distribution and evaluation of the load bearing capacity of the contact.

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Finite element analysis of lightweight concrete-filled LSF walls exposed to realistic design fire

Journal of Structural Fire Engineering ◽

10.1108/jsfe-10-2021-0066 ◽

2022 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Irindu Upasiri ◽

Chaminda Konthesingha ◽

Anura Nanayakkara ◽

Keerthan Poologanathan ◽

Gatheeshgar Perampalam ◽

...

Keyword(s):

Lightweight Concrete ◽

Fire Exposure ◽

Fire Performance ◽

Content Type ◽

Design Fire ◽

Standard Fire ◽

Heating And Cooling ◽

Cooling Phase ◽

Concrete Filling ◽

Design Fires

PurposeLight-Gauge Steel Frame (LSF) structures are popular in building construction due to their lightweight, easy erecting and constructability characteristics. However, due to steel lipped channel sections negative fire performance, cavity insulation materials are utilized in the LSF configuration to enhance its fire performance. The applicability of lightweight concrete filling as cavity insulation in LSF and its effect on the fire performance of LSF are investigated under realistic design fire exposure, and results are compared with standard fire exposure.Design/methodology/approachA Finite Element model (FEM) was developed to simulate the fire performance of Light Gauge Steel Frame (LSF) walls exposed to realistic design fires. The model was developed utilising Abaqus subroutine to incorporate temperature-dependent properties of the material based on the heating and cooling phases of the realistic design fire temperature. The developed model was validated with the available experimental results and incorporated into a parametric study to evaluate the fire performance of conventional LSF walls compared to LSF walls with lightweight concrete filling under standard and realistic fire exposures.FindingsNovel FEM was developed incorporating temperature and phase (heating and cooling) dependent material properties in simulating the fire performance of structures exposed to realistic design fires. The validated FEM was utilised in the parametric study, and results exhibited that the LSF walls with lightweight concrete have shown better fire performance under insulation and load-bearing criteria in Eurocode parametric fire exposure. Foamed Concrete (FC) of 1,000 kg/m3 density showed best fire performance among lightweight concrete filling, followed by FC of 650 kg/m3 and Autoclaved Aerated Concrete (AAC) 600 kg/m3.Research limitations/implicationsThe developed FEM is capable of investigating the insulation and load-bearing fire ratings of LSF walls. However, with the availability of the elevated temperature mechanical properties of the LSF wall, materials developed model could be further extended to simulate the complete fire behaviour.Practical implicationsLSF structures are popular in building construction due to their lightweight, easy erecting and constructability characteristics. However, due to steel-lipped channel sections negative fire performance, cavity insulation materials are utilised in the LSF configuration to enhance its fire performance. The lightweight concrete filling in LSF is a novel idea that could be practically implemented in the construction, which would enhance both fire performance and the mechanical performance of LSF walls.Originality/valueLimited studies have investigated the fire performance of structural elements exposed to realistic design fires. Numerical models developed in those studies have considered a similar approach as models developed to simulate standard fire exposure. However, due to the heating phase and the cooling phase of the realistic design fires, the numerical model should incorporate both temperature and phase (heating and cooling phase) dependent properties, which was incorporated in this study and validated with the experimental results. Further lightweight concrete filling in LSF is a novel technique in which fire performance was investigated in this study.

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Experimental and numerical study on post-fire behavior of high-strength Q460 steel columns

Advances in Structural Engineering ◽

10.1177/1369433216649390 ◽

2016 ◽

Vol 19 (12) ◽

pp. 1873-1888 ◽

Cited By ~ 2

Author(s):

Weiyong Wang ◽

Tianzi Liu

Keyword(s):

Finite Element ◽

Bearing Capacity ◽

Fire Behavior ◽

High Strength ◽

Finite Element Models ◽

Load Bearing Capacity ◽

Steel Columns ◽

Standard Fire ◽

Heating And Cooling ◽

High Strength Q460 Steel

Experimental study and finite element modeling on the structural behavior of high-strength Q460 steel columns after being exposed to ISO-834 standard fire are presented. Two section shapes were considered, namely welded H-shaped section and welded box-section. The experiment composes of two stages: heating and cooling stage of the specimens and compressive test on the specimen after fire exposure. The temperatures experienced in the specimens were recorded during both the heating and cooling phases, as well as the load–deflection curves, load–axial displacement curves, load–rotation curves, load–strain curves, and failure modes in the steel columns were measured during the compressive tests. Three-dimensional finite element models were also established by employing the program ANSYS to study the post-fire behavior of high-strength Q460 steel columns. The finite element models were used to investigate the effects of key parameters on the residual load-bearing capacity of high-strength Q460 steel columns, following exposure to the ISO-834 standard fire. The investigated parameters included heating time, cooling methods, and slenderness ratio. Finally, a simplified design approach was proposed for predicting the residual load-bearing capacity of high-strength Q460 steel columns after being exposed to ISO-834 standard fire.

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Post-Fire Susceptibility to Brittle Fracture of Selected Steel Grades Used in Construction Industry—Assessment Based on the Instrumented Impact Test

Materials ◽

10.3390/ma14143922 ◽

2021 ◽

Vol 14 (14) ◽

pp. 3922

Author(s):

Mariusz Maslak ◽

Michal Pazdanowski ◽

Marek Stankiewicz ◽

Paulina Zajdel

Keyword(s):

Charpy Impact ◽

Water Mist ◽

Heating Regime ◽

Building Structures ◽

Initial State ◽

Slow Cooling ◽

Natural Fire ◽

Development Scenarios ◽

Steel Grades ◽

Fire Conditions

The change in the value of the breaking energy is discussed here for selected steel grades used in building structures after subjecting the samples made of them to episodes of heating in the steady-state heating regime and then cooling in simulated fire conditions. These changes were recorded based on the instrumented Charpy impact tests, in relation to the material initial state. The S355J2+N, 1H18N9T steels and also X2CrNiMoN22-5-3 duplex steel were selected for detailed analysis. The fire conditions were modelled experimentally by heating the samples and then keeping them for a specified time at a constant temperature of: 600 °C (first series) and 800 °C (second series), respectively. Two alternative cooling variants were investigated in the experiment: slow cooling of the samples in the furnace, simulating the natural fire progress, without any external extinguishing action and cooling in water mist simulating an extinguishing action by a fire brigade. The temperature of the tested samples was set at the level of −20 °C and alternatively at the level of +20 °C. The conducted analysis is aimed at assessing the risk of sudden, catastrophic fracture of load-bearing structure made of steel degraded as a result of a fire that occurred previously with different development scenarios.

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PERFORMANCE BASED COUPLED CFD-FEM ANALYSIS OF 3-BAY HIGH INDUSTRIAL HALL UNDER NATURAL FIRE

Applications of Structural Fire Engineering ◽

10.14311/asfe.2015.014 ◽

2016 ◽

Author(s):

Michal Malendowski ◽

Adam Glema ◽

Wojciech Szymkuc

Keyword(s):

Heat Exposure ◽

Fem Analysis ◽

Structural Elements ◽

Fire Load ◽

Natural Fire ◽

Standard Fire ◽

Complex Approach ◽

Main Emphasis ◽

Low Probability ◽

And Performance

In this paper, the main emphasis is put into showing differences between standard fire design of structural elements and performance based approach, that takes into account analysis of structure under natural fire. The exemplary structure is a 3-bay 65,0x110,0 m in plane and 22,0 m high industrial hall with heavy cranes. Because of the significant volume with respect to fire load, there is a low probability that the fully developed fire can occur, nonetheless regarding technological process, a significant local fire could take place and affect the neighbour structure. The most complex approach used in this work is based on coupled CFD-FEM analysis of influence of local fire onto structure.Fire exposure of structural elements is calculated by the coupling scripts, taking into account real heat exposure of section by using adiabatic surface temperature approach.

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Practical method to predict the axial capacity of RC columns exposed to standard fire

Journal of Structural Fire Engineering ◽

10.1108/jsfe-08-2016-0015 ◽

2018 ◽

Vol 9 (4) ◽

pp. 266-286 ◽

Cited By ~ 3

Author(s):

Salah F. El-Fitiany ◽

Maged A. Youssef

Keyword(s):

Concrete Strength ◽

Practical Method ◽

Simple Method ◽

Rc Columns ◽

Content Type ◽

Natural Fire ◽

Rc Structures ◽

Axial Capacity ◽

Standard Fire ◽

Structural Engineers

Purpose Existing analytical methods for the evaluation of fire safety of reinforced concrete (RC) structures require extensive knowledge of heat transfer calculations and the finite element method. This paper aims to propose a rational method to predict the axial capacity of RC columns exposed to standard fire. Design/methodology/approach The average temperature distribution along the section height is first predicted for a specific fire scenario. The corresponding distribution of the reduced concrete strength is then integrated to develop expressions to calculate the axial capacity of RC columns exposed to fire from four faces. Findings These expressions provide structural engineers with a rational tool to satisfy the objective-based design clauses specified in the National Code of Canada in lieu of the traditional prescriptive methods. Research limitations/implications The research is limited to standard fire curves and needs to be extended to cover natural fire curves. Originality/value This paper is the first to propose an accurate yet simple method to calculate the axial capacity of columns exposed to standard fire curves. The method can be applied using a simple Excel sheet. It can be further developed to apply to natural fire curves.

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Fire Behavior of Raw Earth Bricks: Influence of Water Content and Cement Stabilization

10.4028/www.scientific.net/cta.1.792 ◽

2022 ◽

Author(s):

Rafik Isaam Abdallah ◽

Céline Perlot ◽

Hélène Carré ◽

Christian La Borderie ◽

Haissam El Ghoche

Keyword(s):

Water Content ◽

Thermal Instability ◽

Fire Behavior ◽

Standard Fire ◽

Influence Of Water ◽

Cement Stabilization ◽

The One ◽

Raw Earth ◽

Water Contents ◽

Soil And Water

This study focus on the effects of both water content and cement stabilization on the fire behavior of earth bricks. To observe the effect of cement stabilization, two materials are formulated: raw earth with only soil and water, and stabilized bricks with soil, water and cement (3.5% by mass of soil). Since the material’s mechanical strength can strongly influence its fire behavior, the raw bricks were compacted at 50 MPa to reach a compressive strength similar to the one of stabilized bricks. Four different water contents were tested; dry state obtained with oven drying and three others achieved through equalization at 50%, 75% and 100% of relative humidities. Bricks are then subjected to an ISO 834-1 standard fire. Results show that water content has caused a thermal instability behavior on the raw earth bricks after equalization at 50% and 75% relative humidities. Thermally stable bricks displayed a noticeable diffusion of cracks on their heated face. Furthermore, cement stabilization helps to prevent from thermal instabilities.

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